1. Field of the Invention
The present invention pertains to cutting tools and in particular to tools for machining and finishing metal. More specifically, it pertains to tools especially adapted for internal threading and/or grooving of metal.
2. Brief Description of the Prior Art
Cutting tools for machining threads and grooves in metal have existed for many years. Tools for both external and internal machining are well known in the prior art. A common practice, for internal machining, is to fasten the part to be machined in a chuck or vise, to fasten a cutting tool in another chuck or vise of a machine and to rotate one of the chucks relative to the other. With many of such internal cutting tools, the tool includes an elongated bar at the end of which is attached, in some fashion, a replaceable cutting insert. When the cutting insert is broken or worn, it may be removed and replaced with a new or sharpened cutting insert without having to replace the more expensive bar.
Several of the cutting bars of the prior art are provided with an anvil having a recess or groove in which the cutting insert may be received and by which the cutting insert may be clamped between the anvil and the bar. In some of these tools, the anvil is integral with the bar, whereas, in the others, the anvil is a separate member which is removably fastened to the bar.
One of the major problems in internal machining is providing rigidity of the bar and cutting insert mounting. This is particularly a problem in internal threading or grooving of a machine part with a small internal diameter. In order to be received within a part of small internal diameter, the portion of the tool extending thereinto must of necessity have a small cross-section of reduced mass. Furthermore, with commonly used cylindrical bars and anvil mountings, the diameter of the bar must be reduced in order to allow room for radial projection of the cutting insert mounted thereto. This further reduces the mass of the bar and necessarily results in a bar of less rigidity. With reduced rigidity, chatter may occur, resulting in inferior machining and possible breakage of cutting inserts and anvils. Even if chatter does not occur, the bar may flex to such an extent that accurate machining is not obtained.
Another problem associated with internal machining is the inability to machine near the end of a counterbored hole. With the common prior art right-angle mounting of cutting inserts on the bar, the bar anvil or side of the cutting insert may prevent complete depth machining in the counterbore.